Blocking-layer electrode system



Nov. 4, 1941. L. A. L.-ESSELING EIAL 2,261,613

BLOCKING-"LAYER ELECTRODE SYSTEM Filed Jan. 12, 1940 8 l F, 5' i l .4 L; l4

INVENTORS L. A. L ESSEL/NG W. C. VAN GEEL A TTORNE Y Patented Nov. 4, 1 941 I BLOCKING-LAYER ELECTRODE SYSTEM Lndovicus Aumtinns Lambertns Euellngand Willem Christian Van Geel, Eimllloven, Netherlands, assignon to Radio Corporation of America, New York, N. Y.

Application January 12, 1940, Serial No. 313,044

. In Germany January 23, 1939 a 8 Claims. (onus-zoo) This invention relates taa blocking-layer elec- :trode system having flxed electrodes, particularly to act upon' electric high-frequency or termediate-frequency oscillations.

I The invention particularly has for its purpose to establish a good electric contact between the supply conductors for such a system and the'electrodes of the system, avoiding in this case the disadvantages which are frequently inherent as additionalphenomena in known contacts which are good in themselves.

The contacts most known in such systems are latter electrode recessed in it which is filled with the. contact material.

As regards the last-mentioned form of construction, the advantage is obtained that a rigid connection between the contact carrier for one electrode and the opposite electrode is established independently of the intermediate layers (for example, a selenium layer having a blocking spring contacts, with which either a spring directly engages the surface of the electrode system or a solid conductive body engages this surface by means of a'spring. In the case of seriesconnection of blocking-layer electrode systems, as is customary, for example, with rectifiers, the solid body establishing the contact is constituted, for example, either by the carrier plate of the next electrode system or by a cooling plate.

Springs directly engaging the contact surface of the electrode system involve inter alia the inconvenience that oxide formation at the contact pointcan be avoided only with dimculty.

In the case of a rather considerable pressure of the spring, both with directly engaging springs and with intermediate arrangement of solid contact pieces, the disadvantage arises that the correct pressure can be adjusted only with difliculty. Moreover, the exerted pressure may cause damage to the blocking layer and particularly in electrode systems for acting upon electric highfrequency or intermediate-frequency oscillations the draw-back becomes manifest that the properties of the system (for example capacity, blocking capacity) vary due to .the pressure continuously exerted. This is inadmissible, since the circuit arrangements in which the electrode systems are included are designed for unvariable electric values of these systems, said values consequently not being allowed to vary during operation.

It has already been suggested (French Patent 809.216) to pour an electrode of liquid mater al into a body which exhibits a channel and is arranged on the blocking layer, and to provide a supply conductor in this channel. Although in this case considerable advantages are obtained as regards easy realization of a small contact surface, the problem that the properties of the system may vary, for example, due to me hanical forces exerted upon the supply conduntors for the electrodes is yet not dealt with.

The invention consists in that the carrier plate for one electrode is mechanically connected in a rigid manner to a rigid contact-carrier for .the supply conductor of the electrode on the other side of the blocking layer, and that the said contact carrier has an entry channel for the layer and, if desired, a metal layer bearing on the latter), for the contact carrier is directly carried by the carrier-plate for the counter electrode. Such a carrier plate has sufiicient rigidity and it can therefore be said that the distance between the contact carrier and the carrier plate is perfectly fixed by the means stated so that the contact cannot act upon the properties of-the intermediate layers, for example by an exerted pressure.

One advantageous form of construction is characterized by that the contact material used, which fills the entry channel to. the electrode,

' is the same material constituting the surface of the electrode -which is adjacent the contact carrier.

A fully continuous transition is thus obtained between the contact material kept in the entry channel and the material constituting the electrode with which the contact is established. The construction can be made such that the electrode consists of an alloy applied by coating and melting at low temperature and thatiithe channel of the contact carrier whichextends at a short distance over this electrode is filled withthe same alloy in such manner that the material flowed out of the mouth is united with the upper surface of the electrode to form an assembly.

To fasten the contact carrier to the carrier plate for the counter electrode, use may be made without objection of metal parts, the contact carrier itself being manufactured from insulating material. It is advantageous in this case to establish the connection to the exterior by providing a metal bush in the channel which consequently constitutes its wall.

Further measures which can be carried out with advantage are evident from the description of a complete form of construction which will be explained more fully by reference to the accompanying drawing.

An aluminium plate I constitutes the carrier plate for the electrode system. On this plate is a selenium layer 2 whose upper side carries a blocking layer which is so thin that it is not shown in the drawing. The contact carrier is denoted by 3.

The rigid connection between the carrier plate I and the contact carrier 3 which is located on the other side of the blocking layer applied to the electrode 2 is established with the aid of a shell 4 which laterally embracesthe whole electrode system. In the present form of construction the shell is made of brass.

Theflgure further shows that the contact carrier 3 is shaped in the form of a disc and that the entry channel to the underlying electrode system is constituted by a central bore 5. The disc 3 consists of a rigid insulating material, such as pertinax, and the inner wall of the bore 5 is constituted by a metal bush 3 which is constituted by tinned brass in the present example.

Between the contact carrier 3 and the adjacent side of the electrode system there exists a hollow space I, whose diameter is larger than that of the entry channel 3. The entry channel 5 contains the contact material 3 which in the present form of construction is constituted by an alloy of tin, bismuth and cadmium and melts at a temperature a little higher than 100. This alloy was introduced in the liquid condition into the entry channel and, as is shown in the figure, this liquid material has somewhat spread in the hollow space I so that a wide foot 3 has been formed. If thecontactgmaterial 3 would flow out to a further extent, the surface over which this flowing-out would take place is in any case limited by the walls of the hollow space I. It

can be seen that the contact material can be caused to fiow directly on to the blocking layer of the electrode 3 so that this material itself constituted the counter electrode. In this case the surface of this electrod is anyhowlimited by the walls of the hollow space I. In fact, the exact determination of the size of the contact surface between this electrode and the blocking layer is of great importance for a large number of applications of the electrode system, for example as a detector.

In the form of construction shown still another method was used; in fact, an electrode I I was preliminarily applied by coating to the blocking layer of th electrode 2, whose surface was limited with the aid of a templet which has been removed afterwards. The electrode II applied by coating consists of the same material as the contact material 3, that is to say of the above-mentioned alloy. Thus a perfect flowing together of the surfaces is obtained. Although the electrode III and the contact piece I have been provided separately, a continuous assembly is definitely obtained without any transition resistance whatever.

The same result can also be obtained with the use of other materials. If the contact piece I were manufactured, for example, from compressed graphite or from graphite with a binder, a graphit layer could preliminarily be applied directly to the blocking layer of theelectrode 2 v onto the surface of an electrode Il presentfon' this layer. The contact piece 3 could initially.

be provided in the liquid condition by the use of a graphite suspension, from which the suspension agent is removed afterwards, for example by volatilisation.

The hollow space 1 has so large an inner diameter that it contains the whole electrode II.

serves to fix the contact carrier 3 and the carrier plate I for the electrode system in their relative distance, which consequently is effected fully independently of the electrode system 'proper. For this purpose the shell 4 in th example is shaped in the form of an obtuse cone and this with an incline of about 7 at the most, and the discs and 3 constituting respectively the carrier plate for one electrode 2 and the contact carrier are pressed into the. shell in a clamped manner. Due to the small inclination angle of the shell wall, the friction is so great that the pressed parts I and 3 cannot become loose. The edge I2 of the shell 4 is flanged by way of additional measure oi security. Such fianging of a shell at the upper and the lower sides might also independently be used to fix the carrier plate I and the contact member 3 relatively to one another; to ensure the relative distance, in this case a distance piece is provided between these parts. The shell need not be conical in this case.

The shell 4 in the example exhibits a base I3 on which a metal washer I4 is arranged under th carrier plate I, this washer in the present example consisting of copper. This washer has such a diameter that its edges are free from the inner wall of the shell. During pressing in the washer I4 determines the distance of the metal plate I from the base I3 and prevents the metal plate I from being depressed to such an extent that the lower end of the shell is attained where the incline of the wall is greater than 7. The washer I4 also nsures that the metal plate I lies entirely fiat.

It would also be possible to make the washer I4 and the metal plate I in one piece. It is further possibl to make the ring I I and the disc 3 in one piece. In the latter case a hollow space is simply to be recessed at the bottom side of the disc 3.

The bush 3 arranged in the channel I of the contact carrier 3 constitutes a whole with a connecting strip. For this purpose th bush 8' is lengthened till above the disc 3. To prevent torsion of the strip IS, the channel 5 can be, given a non-cylindrical, for example quadratic section. The connecting strip II for the electrode 2 can simply be soldered to the base I3 of the shell 4. The contact carrier 3, the filling 3 of the channel I and the connecting means 4, I3 between the contact carrier and the carrier plate I Jointly constitute a closed assembly. so that the electrode system proper is fully shut off from the surroundings; This shutting of! can still be improved by painting the assembly with an obtu- 1 rating material, for example an artificial resin,

Consequently, the contact can'ier 3 never exerts pressure on the electrode III, not even in the manufacture which will be discussed hereinafter.

The hollow space I in the example was obtained by providing a ring II under the contact carrier 3, whose inner diameter consequently determines the diameter of the hollow space 'I.

or by immersing it into such a material. This is {shutting off from the atmosphere still increases electrode system.

the stability of the features of the blocking-layer I of parts located outside the electrode system, that is to say by means of the shell 4, in which are pressed the carrier plate I and the contact carrier 3. Then the contact material is provided As has already been mentioned, the shell 4 which establishes the connection between the the ring ll.

contact carrier and the surface of the electrode system located under this carrier. Said material is initially capable of being deformed so that it can fill the space between the said parts and engage theseparts and match their shape so that a good conductive contact can be established on the one hand impossible that the rigid contact is interrupted and on the other hand the occurrence of a variable pressure of the contact on the carrier is prevented. Since the contact material is still, it moreover does not undergo deformation.

The influence of variations in the distances due to extension as a result of influences of heat can be obviated in such manner that the coemcient of expansion is taken into account with the choice of the materials and care is taken that the deformations on the spot of the electrode system neutralise each other and consequently no variation in pressure in the layers of the electrode system occurs with change of temperature.

As has been mentioned, the contact material 8 can be poured in the liquid condition into the channel 5. After the construction of the whole, it is also possible, however, to lie a small ball of a material having a low melting point in the channel and to render this liquid by heating.

In the construction of the device described, first the filling disc i4 is laid on the base i3 of the shell 4. Then the carrier plate I together with the layers preliminarily applied to it (selenium layer 2, blocking layer and, if desired, electrode ill) is pressed into the shell 4 until it abuts on the filling disc H. To avoid too great a pressure, use may be made of a die which stands under resilient force and consequently can yield at a given pressure.

Now, the disc 3 is pressed-in. To adjust the correct distance with respect to themetal plate I, use may be made for the die of a stop-piece provided on the die which is so adjusted that the die is held up at the moment that the disc 3 has the correct distance from the shell 4. This distance must exactly correspond to the height of If this ring is made as a separate body, it is to be arranged beforehand.

It would also be possible to use a special distance piece inside the shell 4 instead of the stop piece connected with the press. It is conceivable to use the ring II as a distance piece, but if we wish to proceed very exactly, this is to be avoided, since in this case in assembling a certain pressure is necessarily exerted by the ring upon the blocking layer existing on the selenium electrode 2. It has been found that this pressure also acts upon the properties at the point where the contact piece 8 bears on the blocking layer. Moreover, the properties of the selenium layer may also be influenced by the exertion of a pressure.

The device described. in addition to offering the said advantages. otters the further advantage that it is suitable for mass production and What we claim is:

1. An electrode system for rectifying or controlling electric high-frequency or intermediatefrequency oscillations, comprising a pair of solid electrodes having a blocking layer interposed between them, characterized in that a carrier plate for one of said electrodes is mechanically connected in a rigid manner with a. rigid contact carrier for the supply conductor of the other electrode, said contact carrier having an entry channel which is filled with contact material and adjacent to which the latter electrode is disposed, said contact carrier having associated with it means for providing a recessed hollow space whose diameter is larger than that of the entrychannel of the contact carrier," the diameterof' the hollow space determining the maximum possible spreading of the contact material which is introduced into the entry channel.

2. An electrode system as defined in claim 1, in which the means for providing the recessed hollow space comprises a ring disposed on the under surface of the carrier, the inner diameter of said ring determining the diameter of the hollow space.

3. An electrode system for rectifying or controlling electric high-frequency or intermediateirequency oscillations, comprising a pair of solid electrodes having a blocking layer interposed between them, characterized in that a carrier plate for one of said electrodes is mechanically connected in a rigid manner with a rigid contact carrier for the supply conductor of the other electrode, and a shell shaped in the formof an obtuse cone having an incline of about 7 at the most and having discs pressed therein in a clamped manner, said discs constituting the carrier plate for one electrode and the contact carrier for the supply conductor of the other electrode.

4. An electrode system as defined in claim 3, in which the edge of the shell is flanged over the contact carrier.

5. An electrode system as defined in claim 3. in which the shell is provided with a base on which a metal washer is arranged under the carrier plate, said washer having such a diameter that its edges are free from the inner wall of the shell.

6. An electrode system as defined in claim 3, in which materials are used having such coefficients of expansion that no variation of pressure occurs in the electrode system due to variation of temperature.

7. A blocking-layer electrode system having a pair of fixed electrodes and a blocking-layer inthat the supply conductors can be easily brought terposed therebetween, a metal carrier plate supporting one of the electrodes, a contact carrier of insulating material for the second electrode fastened'to the carrier plate at a given distance from the first electrode by means located outside the electrode system, and a contact material provided between the contact carrier and the second electrode, said contact material being introduced in a molten condition.

8. An electrode system as defined in claim 7 in which the contact material consists of an alloy having a low melting point and is introduced in liquid condition into an entry channel provided in the dontact carrier, the contact material solidilying in the channel in a pile which bears on the surface of one of the electrodes of the system.

LUDOVICU S AUGUSTINUS LALIBERTUS ESSELI'NG. WILLEM CHRISTIAAN VAN GEEL. 

